Characterization of lead lanthanum titanate thin films grown on fused quartz using MOCVD

Abstract

Lead lanthanum titanate (Pb 1− x La x )TiO 3 thin films grown on a fused quartz matrix using the metal-organic chemical vapor deposition (MOCVD) were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman scattering spectroscopy (RSS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. XPS results confirmed the film composition of (Pb 1− x La x )TiO 3 and lanthanum enrichment in top surface layers. XRD study shows that a polycrystalline lead titanate PbTiO 3 film can be grown on fused quartz using MOCVD. For lead lanthanum titanate (Pb 1− x La x )TiO 3 films, a prefered (100) orientation for the films with x values around 0.05–0.17 is observed in XRD patterns, whereas the film with an x value above 0.319 has randomly distributed orientations. A gradual change in the crystal structure moving from tetragonal to cubic arrangement with increasing La concentration is also noted. The shifts of the E(TO) soft mode band in RSS spectra, which depend on temperature are governed by the formula of ω=Aω 0|T−T 0| 1 2 . Infrared vibration absorption bands at 667, 826, 936 and 529 cm −1 were observed and attributed to TiO and PbO stretching vibrations while a band around 500 cm −1 was related to the lanthanum-oxygen stretching vibration in the films, indicating a stronger LaO bonding strength in the film than in its typical oxide, La 2O 3.